1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel where a LaF.sub.3 thin film is deposited on a MgO protective layer of a front substrate and a method for manufacturing the same.
2. Description of the Related Art
In general, display devices are divided into a cathode ray tube and a flat panel display. The flat panel display is thinner and more convenient to carry and consumes less power than the cathode ray tube.
The types of flat panel displays available are a liquid crystal display (LCD), a plasma display panel (PDP), and a field emission display (FED). The PDP is advantageous in embodying a large screen, compensating for the shortcomings of the LCD.
A general plasma display panel includes a rear substrate 1 and a front substrate 8 where lower electrodes 2 and upper electrodes 7 in strips are respectively formed on the facing surfaces of the rear substrate 1 and the front substrate 8, as shown in FIG. 1. The rear substrate 1 has a dielectric layer 3 on which barrier ribs 4 are formed. Spaces separated from each other by the barrier ribs 4 which are adjacent to each other form discharge cells 9, which are filled with an inert gas such as Argon. A phosphor layer 5 is formed on the bottom surfaces of the discharge cells 9 and the side walls of the barrier ribs 4. The dielectric layer 3 and a MgO protective layer 6 are sequentially stacked on the front substrate 8. The MgO protective layer 6 reduces a discharge voltage when discharge occurs in the discharge cells 9 and protects the upper and lower electrodes 2 and 7 in the panel.
The operation of the PDP having the above structure will be briefly described.
When a voltage is applied between the upper and lower electrodes 2 and 7, ultraviolet (UV) rays are generated by gas discharge and excite the phosphor layer 5 coated on the internal surfaces of the discharge cells 9. Then, visible rays are emitted from the phosphor layer 5 due to photoluminescence. At this time, colors are displayed by the red, green, and blue phosphor layers 5 formed inside the respective display discharge cells 9.
However, after the MgO protective layer 6 is vaporized and deposited on the dielectric layer 3 formed on the front substrate 8 in a deposition chamber (not shown), when the front substrate 8 is taken from the deposition chamber to the air, the MgO protective layer 6 reacts with moisture in the air, that is, an OH group. The OH group in air is distributed on the MgO protective layer 6 to a thickness of 5 through 20 nm and reacts with MgO. Accordingly, impurities of Mg(OH).sub.2 are formed on the surface of the MgO protective layer 6. Mg(OH).sub.2 causes the discharge to be nonuniform and increases the discharge voltage, to thus deteriorate the performance of the display panel.
Therefore, recently, when the rear and front substrates are sealed to each other in order to minimize the reaction of the MgO protective layer with moisture, a thermal treatment process is performed together with vacuum exhaustion. However, such a process has a low efficiency of removing moisture and the time required for performing the process or the installation cost increases. Also, it is necessary to further include a vacuum device to prevent moisture in air from reacting with the MgO protective layer.